This invention relates to colored lustrous pigments and to processes for producing same.
Colored lustrous pigments are of increasing importance in varied fields, e.g. in cosmetics or as additions to synthetic resins, lacquers and dyes. Because of the growing acceptance of lustrous pigments, there exists the need for new colors for various markets.
Processes are known wherein dyestuffs are added to lustrous pigments during their production so that, besides the colors resulting from interference phenomena, additional color effects can be achieved. Thus, e.g., according to German Pat. No. 2,124,155, dyestuffs are added during the formation of lustrous pigments based on triazines, urazils and basic lead carbonate, thereby being incorporated into the pigment particles. Furthermore, it is known, e.g. according to Germa (Federal Republic of Germany) Patent No. 1,192,353, that better adhesion of the dyestuffs onto the pigment particles is achieved by producing water-insoluble dyestuffs directly in the suspension which contains the pigment particles, thereby permitting the dyestuff to be deposited in finely-divided form directly upon the pigment particles.
These processes, however, are not satisfactory on a practical scale. For example, only a portion of the dyestuff is fixed onto the pigment particles, and the main amount of the dyestuff instead of precipitating out on the pigment particles, is found in suspension. The dyestuff can also be easily washed off of the pigments with water. Furthermore, in most cases, a non-uniform distribution of the dyestuff on the pigment surface is observed, whereby the properties of the final products, especially their gloss, are strongly impaired.